This application claims the benefit of provisional application Ser. No. 61/163,398 filed Mar. 25, 2009, the complete contents of which are incorporated herein by reference.
This invention relates to a method and device that helps maintain the integrity of a pipe system when subjected to abnormal internal pressures. It is especially useful in drain pipe systems made of cast iron.
In a typical building drain piping system, sections of cast iron drain or DWV (drain, waste and vent) pipe and their fittings are assembled by butting the ends of the pipe sections together and bridging the joints with water-tight rubber or rubber/metal couplings. These abutting pipes and fittings are secured together and sealed with metal band screw clamps tightened to about 60 in-lb of torque to compress the tubular sleeves. This is commonly called a “no-hub” cast iron system.
Building drain or DWV piping is considered a low-pressure application typically operating at about 5 psi or less when in service, Such piping systems are not usually subject to the rigorous engineering of a pressurized pipe system.
However, under “high” pressures, e.g., above 15-20 psi, such as might occur within the piping system when drains become blocked in a multi-story building or under system pressure testing, these joints and fittings have a tendency to move and sometimes separate, with resulting leakage and property damage. The thrust forces involved in causing the separation can vary from a few hundred pounds to several thousand pounds, depending on the size of the pipe and number of floors behind the drain back-up.
At least in part because gravity (the weight of the pipe) does not effectively counter the separation forces where the pipe is running horizontally, such joint failures tend to occur at or near the point where the drain piping changes direction from vertical to horizontal, particularly as commonly occurs at the base of a multi-story vertical “stack” of pipe, such as at the building ground floor. Where the joints at such transitions are able to withstand the pressure and maintain integrity, however, the next and subsequent joints in the horizontal piping at which changes in direction occur may also be subject to the same type of failure.
There is no standard solution to this, and not every building contractor takes the pains to address it. A common method of dealing with the potential problem is to fabricate some kind of “splint” system on-site to reinforce major vertical-to-horizontal transitions in the piping, using bulky and often expensive combinations of threaded rod, fasteners, scrap or fabricated metal or heavy pipe “riser clamps” which are large, usually heavy-gage metal clamps which look like bear traps and which are commonly used to support the weight of vertical pipe runs by resting on the decks of consecutive building floors. There is thus a need for way to restrain movement in the joints adjacent to a bend in the drain/DVW piping, and to reduce the solution down to a simple, standardized, easily transported and installed device, which can be capable of working with a range of pipe sizes, pipe types, and pipe pressures.